Usefulness of Genotype MTBDRplus assay in acid-fast bacilli positive smear specimens in Almeria, Spain.

INTRODUCTION: The urgent need for operational research evaluating test performance in a real-world setting has been highlighted. The purpose of this study was therefore to evaluate the performance of MTBDRplus assay. MATERIALS: According to the reference method, of the 155 clinical specimens with valid results, 147 were susceptible to rifampicin (RIF) and isoniazid (INH), with 4 being multi-drug resistant (MDR) and 4 with isolated resistance to isoniazid (INH). RESULTS: The results of the MTBDRplus assay were 100% concordant for the MDR and mono-resistant to INH specimens. However, the MTBDRplus assay showed a resistance pattern to RIF in one specimen which was classified as susceptible by the reference method. The majority of the specimens (118/75.6%) were also tested using the MTBDRplus method after culture on Lowenstein-Jensen media, showing 100% agreement with the results of the test directly from the specimens. An MTBDRplus test result was available within an average of 8 days. CONCLUSIONS: Overall, MTBDR results showed excellent results when compared with the reference method and achieved a significant time-reduction.

Evaluation of the speed-oligo direct Mycobacterium tuberculosis assay for molecular detection of mycobacteria in clinical respiratory specimens.

We present the first evaluation of a novel molecular assay, the Speed-oligo Direct Mycobacterium tuberculosis (SO-DMT) assay, which is based on PCR combined with a dipstick for the detection of mycobacteria and the specific identification of M. tuberculosis complex (MTC) in respiratory specimens. A blind evaluation was carried out in two stages: first, under experimental conditions on convenience samples comprising 20 negative specimens, 44 smear- and culture-positive respiratory specimens, and 11 sputa inoculated with various mycobacterium-related organisms; and second, in the routine workflow of 566 fresh respiratory specimens (4.9% acid-fast bacillus [AFB] smear positives, 7.6% MTC positives, and 1.8% nontuberculous mycobacteria [NTM] culture positives) from two Mycobacterium laboratories. SO-DMT assay showed no reactivity in any of the mycobacterium-free specimens or in those with mycobacterium-related organisms. Compared to culture, the sensitivity in the selected smear-positive specimens was 0.91 (0.92 for MTC and 0.90 for NTM), and there was no molecular detection of NTM in a tuberculosis case or vice versa. With respect to culture and clinical data, the sensitivity, specificity, and positive and negative predictive values for the SO-DMT system in routine specimens were 0.76 (0.93 in smear positives [1.0 for MTC and 0.5 for NTM] and 0.56 in smear negatives [0.68 for MTC and 0.16 for NTM]), 0.99, 0.85 (1.00 in smear positives and 0.68 in smear negatives), and 0.97, respectively. Molecular misidentification of NTM cases occurred when testing 2 gastric aspirates from two children with clinically but not microbiologically confirmed lung tuberculosis. The SO-DMT assay appears to be a fast and easy alternative for detecting mycobacteria and differentiating MTC from NTM in smear-positive respiratory specimens.

Preliminary evaluation of a new kit for differentiation of Mycobacterium tuberculosis complex species using Speed-Oligo MTBC.

We present the first evaluation of a novel molecular assay, the Speed-Oligo Mycobacterium tuberculosis complex (SO-MTBC), which is based on PCR combined with a dipstick for the differentiation of M. tuberculosis complex (MTBC) members. The results of this assay were compared with findings obtained using the Genotype MTBC assay. In this study, 189 strains of MTBC isolates from 2011 to 2014 were evaluated to determine the MTBC species. Most (174, 92 %) of the strains were identified as M. tuberculosissensu stricto, 7 (3.7 %) as Mycobacteriumbovis, 5 (2.6 %) as M. bovis bacillus Calmette-Guérin, 2 (1.1 %) as Mycobacteriumafricanum and 1 (0.5 %) as Mycobacteriumcaprae; no strains belonged to Mycobacteriummicroti and Mycobacteriumcanettii subsp. The concordance κ coefficient obtained was 0.96 with the results of the Genotype MTBC assay. SO-MTBC may represent a fast and easy-to-use alternative for differentiating among MTBC subspecies in laboratories with standard equipment.

Selecting criteria for improving results of an immunochromatographic assay for Mycobacterium tuberculosis complex identification from BacT/ALERT cultures.

We describe a combined macro and microscopic criteria for rapid presumptive differentiation between Mycobacterium tuberculosis complex (MTC) and nontuberculous mycobacteria (NTM) evaluated by two independent observers. This strategy achieved rapid MTC identification in most cases (95.8% expert observer and 91.6% novice observer) with significant savings compared to more expensive and unnecessary tests.